Field of the Invention
The present invention relates to rock crushing machinery and specifically to a jaw type crusher including two opposing jaws, namely, an adjustable jaw in cooperation with a moveable swing jaw.
Description of Related Art
Rock crushing machinery is used to reduce large rocks and boulders into smaller rocks, gravel, or rock dust for use in construction and building industries. Hard rock generally refers to rock materials that are hard, tough, abrasive, and have low friability, such as materials produced from shot rock or gravel quarries. As such, the crushing machinery is often provided in remote locations, such as quarries or construction sites.
One type of crushing machinery well suited for reducing the size of larger hard rocks is a gravity fed jaw crusher, such as the jaw crusher disclosed in U.S. Pat. No. 6,375,105 to Haven et al. A jaw crusher includes a moveable jaw configured to cooperate with a stationary jaw. The two jaws are arranged to form a v-shaped crushing chamber disposed between crushing surfaces of the stationary and moveable jaws. The moveable jaw is coupled to an eccentric shaft through a pitman. Rotational motion of the shaft is transferred to the moveable jaw, causing linear reciprocating motion of the moveable jaw in a generally vertical direction. The motion of the moveable jaw forces the rock material against the stationary jaw as gravity causes the rock material to move downward through the crushing chamber. The crushed rock material is expelled from the chamber through a narrow opening at the bottom of the crushing chamber. The width of the narrow opening is defined as the closed side setting. The closed side setting can be adjusted using an adjustment mechanism, such as a hydraulic ram, coupled to the bottom of the moveable jaw through a toggle plate. The closed side setting may also be temporarily increased to permit non-crushable material, such as iron or other metal deposits, to pass through the crushing chamber. The closed side setting may then be returned to the previous width to continue operation.
While jaw crushers including hydraulic systems for adjusting the closed side setting are known, it has been recognized that such hydraulic systems contribute to increased wear and reduced life span for elements of the crusher. Particularly, adjusting the position of a toggle beam or toggle plate driven by the hydraulic ram inward to decrease the closed side setting of the crusher is accomplished by increasing the attack angle of the moveable jaw. Attack angle is defined as the trajectory or angle of displacement of a lower portion of the moveable jaw at the closed side setting during a crushing cycle. Increasing the attack angle reduces the crushing component of the jaw and increases the wear component of the jaw. In addition, continually altering the attack angle of the moveable jaw contributes to uneven wear along the length of the toggle plate and width of the jaw, which further reduces useful life of the machinery. Therefore, there is a need for a jaw crusher capable of adjusting the closed side setting without causing a corresponding increase in the attack angle of the moveable jaw. There is similarly a need for a jaw crusher that wears consistently and predictably following prolonged use so that the need for maintenance and replacement parts can be easily predicted. The presently invented crusher is configured to address such issues.